The eelgrass in Casco Bay has declined more than 50 percent since 2018.
In this undated photo provided by the Massachusetts Division of Marine Fisheries, an American lobster shelters in an eelgrass meadow off shore from Manchester-by-the-Sea, Massachusetts. Credit: Tay Evans / Massachusetts Division of Marine Fisheries via AP

A critical marine habitat is rapidly declining off the Maine coast.

It’s happening so fast that experts said it’s been cut in half in only about four years.

Mike Doan, a staff scientist at Friends of Casco Bay, is concerned about the recent loss of eelgrass in Casco Bay.

“Eelgrass is a true flowering perennial, a true plant, not a seaweed,” Doan said. “It’s found just offshore, just below low tide out to about 20 feet of water.”

A 2022 report conducted by the Maine Department of Environmental Protection shows staggering results.

“They found that the amount of eelgrass in Casco Bay has been reduced by over half, by 54 percent since the last time they mapped the eelgrass back in 2018,” Doan said.

The reduction in eelgrass creates concern for the living species in these waters.

“To lose over half your bed in just over four years is something I’ve become concerned with and it does mean that we’re losing important habitat for young marine organisms,” Doan said.

It could affect one of Maine’s largest industries, too.

“You’re worried about the effect that will have on lobster populations, on other populations that really require that important eelgrass as habitat,” Doan said.

Scientists have some ideas about why this is happening.

“Too much nutrients, too much nitrogen in the water stimulates the growth of things like algae, phytoplankton,” Doan said. “Too much of that can cloud the water and make it hard for eelgrass to survive.”

Doan said climate change and the recent warming of Casco Bay are other reasons why eelgrass is declining.

There are a few possible solutions to expand the coverage of eelgrass.

“You can increase the amount of eelgrass in the bay by bringing it in from somewhere else. If we can do that with higher heat tolerant plants, that may be a way to go,” Doan said.

Conservation moorings are another possible solution, as this will not physically disturb eelgrass as much.